The present application is the national stage under 35 U.S.C. 371 of PCT/DK99/00296, filed Jun. 4, 1999.
The present invention relates to a shock-absorbing horseshoe with a resilient intermediate layer positioned between a rigid upper part for abutment on the underside of the hoof of the horse and a rigid under part extending at least under a part of the upper part, the upper part and the under part being in rigid mechanical connection with each other solely at the front edge of the shoe.
In a horseshoe of this type known from DK-C-19284 the backwards facing branches of the upper part and the under part of the double horseshoe are substantially of equal length and are connected near their rear ends by means of bolts screwed into threaded bores in the under part and extending somewhat into the prebored holes in the upper part, the resilient intermediate layer being positioned as a resilient ring around each bolt between the under part and the upper part. In this design the shock-absorbing effect of the intermediate layer is considerably impaired by the bolt heads positioned under the bottom side of the under part.
Moreover, as this known horseshoe is secured to the hoof solely by nailing through side edge portions of the upper part outside the narrower under part, the shoeing is made difficult, and the missing intermediate layer in the major part of the interspace between the upper part and the under part requires high rigidity of these parts and a solid, mechanical connection, for instance by welding, between the upper and under parts at the front edge of the shoe, which further impairs the resiliency aimed at.
In an embodiment of a horseshoe known from WO 92/17059, attempts have been made to avoid these drawbacks by placing a shock-absorbing intermediate layer of silicone rubber in the entire interspace between an upper part and an under part consisting of two aluminium layers. The comparatively soft intermediate layer entails that for lack of other mechanical connection means between the upper part and the under part, such connection should be established by means of fastening nails. As aluminium per se is not a particularly well wearing material, there is a considerable risk that the desired shock-absorbing effect will decrease in a short time or be completely eliminated when the nailheads touch the substratum.
In view of this prior art, the object of the invention is to provide a horseshoe of the type stated, which has a simple construction enabling manufacture at a competitive price and gives a substantially improved dampening at impact of the horse hoof against the substratum, and at the same time a particular stable connection with the substratum at the take-off of the hoof is attained as well as a safe securing of the shoe to the hoof without any risk that the individual parts of the shoe will fall apart during use, which may lead to severe damages to the horse.
To meet this object, the shock-absorbing horseshoe is according to the invention characterized in that the under part extends substantially in parallel with the upper part, that the resilient material completely fills out the interspace between the upper part and the under part and is secured thereto, and that openings are provided in the under part, said openings allowing passage of a nailhead of a per se conventional fastening nail in such a manner that the securing of the horseshoe to the hoof by means of such nails is accomplished solely by the abutment of the nailhead on the resilient intermediate layer and by the resilient compression of said layer.
Simultaneously with the fact that the rigid mechanical connection known per se between the upper part and the under part at the front edge ensures a good connection from the hoof through the shoe and down to the substratum at take-off, the fact that the resilient layer fills out completely the interspace between the upper part and the under part entails an optimal shock-absorbing effect in such a manner that the upper part and the under part, in particular at the backwards facing branches of the shoe parts, may spring against and away from each other by the resilient deformation of the intermediate layer.
As the impact of the hoof against the substratum starts at the rear edges of the shoe, the need for shock-absorption is greatest in these places. By the invention a good shock-absorbing effect is ensured at the rear edge of the hoof, where the two metal parts may move fairly freely against one another without being hindered by the rigid mechanical connection at the front edge.
Whereas it has been a problem in connection with the nailing of conventional embodiments of shock-absorbing horseshoes that the fastening nails by the natural compression of the shock-absorbing intermediate layer at each step will become too long which may entail a risk that impurities may penetrate between the hoof and the upper side of the shoe and that the nails may work themselves out of the hoof, the invention has the effect that at the nailing a certain spring-compression of the intermediate layer takes place, whereby the shoe is brought into spring-tensional abutment on the under side of the hoof, and the risk that impurities may penetrate between the hoof and the shoe or that the nails will work themselves out of the hoof is eliminated, the safe securing of the shoe to the hoof being simultaneously ensured under all conditions, also in case of horses with weak hooves.
The upper part and the under part may be made from any suitable material having the required rigidity and wearability, but typically a metal with good wearability and good working properties like for instance steel is chosen.
The shock-absorbing material in the intermediate layer may be resilient plastics and rubbers which have good working properties and which by moulding may be brought to adhere well to the surface of the upper and under parts. Polyurethane (PU) has in particular turned out to be a suitable material.
Advantageous embodiments of the shock-absorbing horseshoe according to the invention are stated in the dependent claims.
In a method preferred for the manufacture of the horseshoe according to the invention the upper part and the under part are cut or punched from sheet material, preferably steel sheet, following which the intermediate layer is manufactured by embedding shock-absorbing, resilient material directly into the interspace between the upper part and the under part.